1. Field of the Invention
The subject invention generally pertains to electric motors with plastic housings and more specifically to ground strap for such a motor.
2. Description of Related Art
Motors, particularly for residential or commercial appliances such as vacuum cleaners, carpet cleaners, etc. are preferably grounded to prevent electrical shock to the user should a short circuit occur in the motor. For greatest protection, it is best to ground both the stator and the rotor (armature) of the motor. This is readily accomplished when the stator and rotor are supported by a housing or bracket made of cast aluminum or other electrically conductive material. In such cases, a ground wire is simply attached somewhere to the housing. Cast aluminum housings, unfortunately, are often more expensive and heavier than plastic ones, so some effort has been made to ground motors that have plastic housings.
U.S. Pat. Nos. 4,698,534 and 4,621,991, for example, disclose a motor supported by a plastic bracket wherein the rotor is grounded by a disk/clip assembly that is pinched or simply jammed between the plastic bracket and the rotor's bearing. Although assembling such a connection may be quick and easy, motor vibration and fatigue may eventually diminish electrical continuity between the clip and the bearing. Nonetheless the design offers the advantage of being able to have the clip extend to where it can be crushed or clamped between the stator and the plastic bracket thereby grounding the stator as well.
U.S. Pat. No. 5,313,129 discloses a means for grounding a rotor by connecting a ground wire to the rotor's bearing. Although the rotor appears to be grounded, it is not clear whether the stator is grounded. It appears that grounding the stator would require additional structure.
For motors whose housing or bracket is made of plastic, the stator can be grounded by welding a ground lug or wire directly to the side of the stator. Although effective, such a method requires additional equipment and labor.
Consequently, there is a need for an easy, inexpensive way to ground both the rotor and the stator of a motor that has a plastic housing and do so with a minimal number of parts.